We use a generalized refractive index that includes diffraction effects to show that the Gouy phase shift can be seen as an intensity averaged optical path difference between the generalized eikonal and the geometrical eikonal. This approach generalizes previous treatments to include the effects of phase distortion and confirms the role of transverse spatial confinement in the Gouy shift.
© 2006 Optical Society of America
Jun Yang and Herbert G. Winful, "Generalized eikonal treatment of the Gouy phase shift," Opt. Lett. 31, 104-106 (2006)